Axle driving unit for a lawn tractor

ABSTRACT

An axle driving unit having a housing ( 21,22 ) for supporting a first axle ( 17 ) for mounting thereon a first driving wheel ( 3 L), and a longer second axle ( 18 ) for mounting thereon a second driving wheel ( 3 R). The axle driving unit is eccentrically mounted on a body frame ( 1 ) in proximity to the first driving wheel ( 3 L). A speed change transmission (T) is disposed in an enlarged region of the housing that extends substantially perpendicularly with respect to the axles ( 17,18 ). The axle driving unit can thus be easily disposed to the side of a chute ( 6 ) of a rear-discharge type lawn tractor.

This application is divisional of application Ser. No. 08/875,724;Filed: Aug. 4, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an axle driving unit suitable for usewith a rear-discharge lawn tractor having a mower located beneath thebody of the tractor between the front and rear wheels.

2. Related Art

U.S. Pat. No. 3,969,876 discloses a conventional lawn tractor having arear discharge system, which has a mower driven by a prime mover mountedon it, and a leaf blower loaded on the rear portion of the tractor. Therear discharge system disposes a chute, for discharging lawn grass cutby the mower, longitudinally between the left and right rear wheels. Therear discharge system has no projection to the outside of the body ofthe tractor. The cut lawn grass is discharged directly rearwardly of thetractor. This has the advantage of eliminating equipment, such as anauxiliary suction fan.

However, because the space between the left and right rear wheels isvery narrow, it is very difficult to laterally juxtapose therebetweenthe cut grass chute and an axle driving apparatus. As disclosed in U.S.Pat. No. 3,969,876, a hydraulic stepless speed change transmission and adifferential gear constituting the axle driving unit are separated andare housed in separate housings. The differential gear is disposed inthe narrow space between the wheels, and the transmission is disposed atanother position on the body of the tractor. The output shaft of thehydraulic stepless speed change transmission and differential gear areconnected by a chain belt mechanism. Accordingly, the axle driving unithas the disadvantages of a high manufacturing cost and a long assemblytime. Also, since one axle, through which the cut grass chute passes, ismuch longer than the other axle, this design has the furtherdisadvantage that the one longer axle is easy to deflect. Accordingly,the life span of a bearing for the one longer axle provided at thedifferential gear is reduced.

An axle driving unit which houses in a common housing a hydraulicstepless speed change transmission and a differential gear fordifferentially connecting a pair of axles and integrates them iswell-known, as disclosed in, for example, U.S. Pat. Nos. 4,914,907 and4,932,209. In these patents, the transmission comprises a combination ofa variable displacement type hydraulic pump and a fixed displacementhydraulic motor. The hydraulic pump and motor are mounted side by sideand longitudinally of the axle with respect to an L-like-shaped centersection, whereby the entire axle driving unit is larger in widthlongitudinally of the axle. Hence, the axle driving unit of this designinterferes with the chute of a lawn tractor which has a rear dischargesystem. As a result, the chute cannot be disposed between the left andright rear wheels.

SUMMARY OF THE INVENTION

The axle driving unit of the present invention is constructed so that afirst shorter axle that mounts a first driving wheel, and a secondlonger axle that mounts a second driving wheel are supported by ahousing provided on a body frame. The housing is attached to the tractorbody frame so that it is eccentric or offset to be in proximity to thefirst driving wheel. The housing is provided with an enlarged regionextending forward at approximately a right angle with respect to theaxles. A hydraulic stepless speed change transmission is provided in theenlarged region. As a result, the axle driving unit of the presentinvention can be easily disposed laterally of (or to the side of) thechute of a lawn tractor of the rear discharge type.

In order to improve the operating efficiency of the hydraulic steplessspeed change transmission, it is desirable to construct the transmissionso that it is a hydraulic stepless system fluidly connecting thehydraulic pump and hydraulic motor to each other. In this case, thehydraulic pump can be disposed in the enlarged region, smaller in widthand spaced apart from the axle, and the hydraulic motor can be disposedin proximity to the axle.

In the enlarged region are provided a pump mounting surface and a motormounting surface disposed substantially perpendicular or rectangularwith respect to each other for mounting the hydraulic pump and hydraulicmotor. It is preferable that the hydraulic pump is mounted onto the pumpmounting surface so that an input shaft connected to the hydraulic pumpis oriented approximately vertically with respect to the axles, and thehydraulic motor is mounted onto the motor mounting surface so that anoutput shaft connected to the hydraulic motor is oriented approximatelyhorizontally with respect to the axles. In a lawn tractor that includesa prime mover having a vertical crankshaft, the input shaft of thetransmission can be connected therewith by use of a simple belttransmitting mechanism. The output shaft of the transmission can beconnected with the axle by use of an inexpensive spur gear having a lowmanufacturing cost.

Bearing means are provided in the housing for supporting the first andsecond axles. A pair of bearing holding portions for supporting distalportions of the first and second axles define the width of the housingto be smaller than the length of the housing including the enlargedregion. As a result, the enlarged region is elongated so that the chutecan have as large a cross-sectional area as possible.

It is desirable that the second longer axle be supported at anintermediate portion thereof by a bearing device provided on the tractorbody frame. As a result, the second longer axle is stably supported. Itis also desirable that the second axle be composed of at least two axleparts separably connected with each other through a coupling. Hence, theaxle driving unit becomes superior in assembly efficiency andtransformation efficiency. The axle to which the other (first) drivingwheel is mounted is stably supported by a bearing device provided on thetractor body frame.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description when the sameis read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a side view of a lawn tractor of the present invention,

FIG. 2 is a cross sectional view of the lawn tractor of FIG. 1 takenalong line 2—2,

FIG. 3 is a cross sectional view taken along line 3—3 in FIG. 2,

FIG. 4 is a cross sectional view taken along line 4—4 in FIG. 3 showinga first embodiment of the axle driving unit, from which an upper halfhousing is removed,

FIG. 5 is a sectional view taken on the line 5—5 in FIG. 4,

FIG. 6 is a sectional view taken on the line 6—6 in FIG. 4,

FIG. 7 is a sectional view taken on the line 7—7 in FIG. 4,

FIG. 8 is a sectional view taken on the line 8—8 in FIG. 4,

FIG. 9 is a sectional view taken on the line 9—9 in FIG. 8,

FIG. 10 is a sectional view taken on the line 10—10 in FIG. 4,

FIG. 11 is a perspective view of a center section of the presentinvention,

FIG. 12 is a partially sectional plan view of a second embodiment of theaxle driving unit, from which an upper half housing is removed,

FIG. 13 is a sectional view taken on the line 13—13 in FIG. 12,

FIG. 14 is a sectional view taken on the line 14—14 in FIG. 12,

FIG. 15 is a sectional view taken on the line 15—15 in FIG. 12,

FIG. 16 is a perspective view of a center section of the secondembodiment,

FIG. 17 is a partially sectional plan view of a third embodiment of theaxle driving unit, from which an upper half housing is removed,

FIG. 18 is a sectional view taken on the line 18—18 in FIG. 17,

FIG. 19 is a perspective view of a center section of the thirdembodiment,

FIG. 20 is a sectional side view of a fourth embodiment of the axledriving unit,

FIG. 21 is a sectional plan view taken on the line 21—21 in FIG. 20,

FIG. 22 is a sectional front view taken on the line 22—22 in FIG. 21,

FIG. 23 is a sectional side view of a fifth embodiment of the axledriving unit,

FIG. 24 is a sectional plan view taken on the line 24—24 in FIG. 23,

FIG. 25 is a sectional front view taken on the line 25—25 in FIG. 23,

FIG. 26 is a sectional side view of a sixth embodiment of the axledriving unit,

FIG. 27 is a sectional plan view taken on the line 27—27 in FIG. 26,

FIG. 28 is a sectional front view taken on the line 28—28 in FIG. 26,

FIG. 29 is a sectional side view of a seventh embodiment of the axledriving unit,

FIG. 30 is a sectional plan view taken on the line 30—30 in FIG. 29, and

FIG. 31 is a sectional front view taken on the line 31—31 in FIG. 29.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description of the various embodiments, description ofparts designated with the same reference numerals will not be repeated,unless specifically noted otherwise. FIGS. 1 through 3 show a lawntractor of the present invention with an engine E mounted on the frontof body frame 1 and freely steerable left and right (or front) wheels 2suspended under the front of body frame 1. An axle driving unit providedwith left and right driving (or rear) wheels 3L and 3R is suspended atthe rear of body frame 1. A grass catcher 4 is mounted to the rear endof body frame 1, and a mower 5 is attached beneath the body of thetractor between the front and rear wheels through an elevation device(not shown). Mower 5 is connected at a rear discharge port 5 a thereofwith an inlet port of catcher 4 through a chute 6. Chute 6 extendsslantwise upwardly from the rear discharge port 5 a of the mower 5,passes laterally or to the side of the axle driving unit and between theleft and right rear driving wheels 3L and 3R so as to be connected tothe inlet of catcher 4. Accordingly, lawn grass cut by mower 5 is blownrearwardly to pass between left and right rear driving wheels 3L and 3Rthrough chute 6, and is then stored in catcher 4. The lawn tractorpreferably includes a height-adjustable seat that can be raised andlowered.

As shown in FIG. 1, two pulleys 8 and 9 are fixed onto an output shaft 7of engine E. Pulley 8 transmits a driving force through a belt 10 to athird pulley 12 fixed onto an input shaft 11 of mower 5, therebyrotating cutter blades 5 b of mower 5 (see FIG. 2). The other pulley 9is adapted to transmit a driving force through a belt 13 to a fourthpulley 15 fixed onto a pump shaft or input shaft 29, projecting upwardlyfrom a housing for the axle driving unit. Reference numeral 16designates a cooling fan fixed to pulley 15 in order to cool the axledriving unit.

As shown in FIG. 3, the axle driving unit is suspended from a firstmounting member 1 a and a second mounting member 1 b, both parts of bodyframe 1. The axle driving unit is eccentrically disposed toward one ofthe two sides of body frame 1. FIG. 3 shows the axle driving unitdisposed in a position displaced toward driving wheel 3L relative to thecenter of the space between left and right driving wheels 3L and 3R. Theleft side of the housing of the axle driving unit is fixed to firstmounting member 1 a, and the right side to second mounting member 1 bthat downwardly extends from a laterally intermediate portion of firstmounting member 1 a. As shown in FIG. 3, body frame 1 of the tractorincludes first mounting member 1 a provided longitudinally of body frame1 and at a portion adjacent to the inside of driving wheel 3L. Thesecond mounting member 1 b is suspended from about the center of thespace between driving wheels 3L and 3R. A bearing 20 is provided at aportion of body frame 1 adjacent to the inside of driving wheel 3R.

The housing for the axle driving unit comprises an upper half housing 21and a lower half housing 22 joined to each other through a peripheraljoint or junction surface. When the housing is mounted in an operatingposition on body frame 1 of the tractor, the joint surface issubstantially horizontally disposed.

Shorter first axle 17 projects from the left side of the housing for theaxle driving unit, and longer second axle 18 projects from the rightside of the housing. Driving wheel 3L mounts at one axial end of firstaxle 17, and driving wheel 3R mounts at one axial end of second axle 18.

A first mounting boss 210 a is formed at a portion of the axle drivingunit housing positioned near the distal portion (portion closest to theaxle driving unit) of first axle 17, and a second mounting boss 210 b isformed at the portion of the housing positioned near the distal portionof second axle 18.

First mounting member 1 a is connected to first mounting boss 210 a, andsecond mounting member 1 b is connected to second mounting boss 210 b.Thus, the housing is eccentrically mounted in the working or operatingposition, offset to one side toward driving wheel 3L. Such a layoutensures a sufficiently wide space between the axle driving unit housingand driving wheel 3R so that chute 6 can be offset from the center ofthe tractor body. As a result, the axle driving unit and chute 6 can bearranged laterally, side by side each other within body frame 1. Thisenables chute 6 to longitudinally extend within body frame 1.

Second axle 18 is supported at the distal portion thereof (18 a) by thehousing, and at an intermediate portion of a longer portion (18 b)projecting outwardly from the housing by a bearing 20. Hence, thedistance between the bearing for supporting the distal portion of firstaxle 17 and that for supporting the distal portion of second axle 18 canbe greatly reduced, thereby reducing the width W of the axle drivingunit housing. Consequently, chute 6 can be designed with a relativelyincreased cross-sectional area.

Alternatively, second axle 18 may be formed as one long axle. However,it is favorable for assembly of the axle driving unit and facilitationof transportation to divide axle 18 into part 18 a supported at thehousing, and part 18 b supported by bearing 20, as shown in FIG. 3.Parts 18 a and 18 b are connected by a coupling 19.

FIGS. 4-11 show the construction of an axle driving unit forspeed-change-driving rear driving wheels 3L and 3R. The housing of theaxle driving unit is formed by connecting upper half housing 21 andlower half housing 22 with each other. Lubricating oil is charged intothe housing, and is used as operating oil for a hydraulic stepless speedchange transmission T to be discussed below. First axle 17 and part 18 aof the second axle are rotatably supported in upper half housing 21positioned above the joint surface. As shown in FIG. 10, cylindricalbores 211 are formed at left and right side walls of upper half housing21 to form first bearing supports, respectively. Rolling bearings 100fitted into cylindrical bores 211 support the distal portion of firstaxle 17 and part 18 a of second axle 18, cylindrical bores 211 beingclosed at their outer ends with oil seals.

As best seen in FIG. 10, semicircular concave circular-arc surfaces 212are formed on the inner surface of an upper wall of upper half housing21. On the inner surface of lower half housing 22 are integrally formedprojections 220 that project beyond the joint surface. Semicircularconcave circular-arc surfaces 221 are formed at the end surfaces ofprojections 220 that are positioned opposite to concave surfaces 212,respectively, to form a pair of second bearing holders. Bushings 101 areinserted into the second bearing holders, so that bushings 101 supportthe base ends of first axle 17 and part 18 a of second axle 18,respectively.

As shown in FIG. 10, concave circular-arc surfaces 213 larger in radiusthan surfaces 212 are formed in concave circular-arc surfaces 212, andconcave circular-arc surfaces 222 larger in radius than surfaces 221 areformed in concave circular-arc surfaces 221. Concave circular-arcsurfaces 213 and 222 are combined to form annular cavities. Rollingbearings (not shown) may be built-in to the cavities, instead of theaforesaid bushings 101, to support the base ends of first and secondaxles 17 and 18. The choice of bushings or bearings depends upon thesize of the load applied to axles 17 and 18. When the load is small,bushings 101, as shown in the embodiment of FIG. 10, are used to reducemanufacturing cost. When the load is large, the rolling bearings (notshown) are used to increase the support strength for the axles.

As shown in FIG. 10, first axle 17 and part 18 a of second axle 18 abutconcentrically against each other in the housing, differentiallyconnected to each other by a differential gear 23 contained in thehousing. Axle 17 and part 18 a of axle 18 project laterally outwardlyfrom the housing.

As best seen in FIGS. 8 and 10, an input gear 48 larger in width thandifferential gear 23 has at the center a through-bore 480. The base endsof first axle 17 and part 18 a of second axle 18 are inserted intothrough-bore 480 to be supported by input gear 48. Bevel gears 49,spline-engaged with first axle 17 and part 18 a of second axle 18, andinput gear 48 prevent axial movement of the axles. Pinions 50 engageablewith bevel gears 49, and through-bores 481 for containing thereinpivotal pins 51 for pinions 50, are provided at both sides of input gear48. A flat portion formed at the circumferential surface of the end ofeach pivotal pin 51 abuts against a flat portion provided at eachthrough-bore 481, thereby restraining each pivotal pin 51 from rotating.Accordingly, differential gear 23 is formed from a smaller number ofparts.

The front portions (portions toward the front or forward end of the lawntractor) of upper and lower half housings 21 and 22 are enlarged in adirection perpendicular to the longitudinal axes of the axles. Thehousing of the axle driving unit is therefore longer (length L1) than itis wide (width W; see FIG. 4). A center section 25 for a hydraulicstepless speed change transmission T is mounted in the enlarged region.As shown in FIG. 11, center section 25 is a single and elongated piecehaving an upper surface 250 and a side surface 251 which are adjacentand perpendicular to each other. A pump mounting surface 40 is formed atthe front portion (toward the front or forward end of the lawn tractor)of upper surface 250 for mounting thereon a hydraulic pump. At the rearportion of side surface 251 a motor mounting surface 41 is formed formounting a hydraulic motor. As shown in FIG. 8, pump mounting surface 40and motor mounting surface 41 are partially overlapped with each otherby a longitudinal length OL. The center of motor mounting surface 41extends in parallel to pump mounting surface 40 and is offset downwardlytherefrom by a height H1.

As shown in FIG. 11, housing mounting faces 42 are formed on uppersurface 250 of center section 25, approximately level with mountingsurface 40. Therefore, housing mounting faces 42 can be ground when pumpmounting surface 40 is ground, so that the processing time for the pumpmounting surface can be reduced. Bolt insertion bores are provided athousing mounting faces 42 and center section 25 is fixed to the innerwall of the enlarged region of upper half housing 21 through connectingbolts inserted into the bores. Pump mounting surface 40 of centersection 25 extends horizontally with respect to the axles, and isdisposed spaced apart from the axles. Motor mounting surface 41 extendsvertically with respect to the axles, and is disposed in proximity tothe axles.

Alternatively, pump mounting surface 40 and motor mounting surface 41may be provided integral to the inner wall by increasing the thicknessof the inner wall in the enlarged region of lower half housing 22.However, as shown in this embodiment, it is preferable to use centersection 25 separate from the housing to facilitate processing of thehousing, and to prevent oil from leaking out of the housing.

As shown in FIG. 5, a valve plate 102 is mounted onto pump mountingsurface 40. A cylinder block 36, constituting the hydraulic pump, isrotatably disposed on valve plate 102. Pistons 36 a are fitted into aplurality of cylinder bores of cylinder block 36, for reciprocatingmovement through biasing springs. Pump shaft 29 engages with a splinebore provided on the rotary axis of cylinder block 36. Pump shaft 29 isrotatably supported by upper half housing 21 and pump mounting surface40. Pulley 15 is fixed to a projection of pump shaft 29 projectingoutwardly from upper half housing 21. The heads of pistons 36 a abutagainst a thrust bearing 28 a of a movable swash plate 28, therebyforming an axial piston type variable displacement hydraulic pump.Alternatively, the hydraulic pump may be of a radial piston type or agear type.

Pump shaft 29 is inserted into a longitudinally extending through-boreformed at the axial center of movable swash plate 28. A convexcircular-arc surface is formed at the rear of movable swash plate 28,and slidably contacts with a concave circular-arc surface formed at theinner surface of the upper wall of upper half housing 21. As a result,movable swash plate 28 is movable in a longitudinal slantwise directionalong the concave circular-arc surface. As movable swash plate 28 moveswith respect to the rotary axis of cylinder block 36 along the contactsurface, the amount and flow direction of oil discharged from thehydraulic pump changes. As shown in FIG. 5, a control shaft 35 formovably operating movable swash plate 28 extends horizontally and isrotatably supported by a lid 38 that closes a side opening of upper halfhousing 21. At an outer end of control shaft 35 is fixed a control lever35 a that is connected in association with a speed change operating tool(not shown). At an inner end of control shaft 35 is fixed a base of aswinging arm 35 b. A ball 37, fixed to the utmost end of swinging arm 35b, engages through a joint block with an engaging groove 28 b of movableswash plate 28, control shaft 35 being rotated for movement of movableswash plate 28.

Movable swash plate 28 shown in this embodiment is of a cradle type thatmoves slantwise along the concave circular-arc surface of the innersurface of the upper wall of upper half housing 21. To enable atrunnion-type swash plate to be mounted instead of cradle-type swashplate 28, a bearing bore is positioned on the same axis as control shaft35 at a portion of the inner wall of upper half housing 21. Where thetrunnion-type movable swash plate is used, each trunnion shaft issupported by the bearing bore and lid 38. The cradle-type movable swashplate is advantageous in that it is inexpensive to produce, while thetrunnion-type is advantageous in that it requires a decreased operatingforce. Swash plates of both types are easily exchangeable.

Referring to FIG. 6, a valve plate 103 is mounted onto motor mountingsurface 41 formed on side surface 251 of center section 25. A cylinderblock 44 of the hydraulic motor is rotatably disposed on plate 103. Aplurality of pistons 44 a are fitted for reciprocating movement into aplurality of cylinder bores of cylinder block 44.

The heads of pistons 44 a abut against a thrust bearing 45 a at a fixedswash plate 45, fixed between upper half housing 21 and lower halfhousing 22. A motor shaft 24 engages with a spline bore provided on therotary axis of cylinder block 44 to form an axial-piston type fixeddisplacement hydraulic motor. Alternatively, the hydraulic motor may beof a radial piston type or a gear type.

The rotation axis of cylinder block 44 is positioned in the same planeas the joint surface of the upper and lower half housings. One end ofmotor shaft 24 is supported by motor mounting surface 41, the other endbeing supported by a bearing sandwiched between upper half housing 21and lower half housing 22.

When the hydraulic pump and the hydraulic motor are disposed on a centersection having the configuration described above, pump shaft 29 andmotor shaft 24 are perpendicular to each other. Pump shaft 29 is offsetfrom motor shaft 24 by a length L2 in the direction apart from the axles(see FIG. 8).

As shown in FIGS. 4, 9, and 11, a pair of kidney-shaped ports 40 a and40 b is open on pump mounting surface 40 of center section 25 to take inor discharge oil in cylinder block 36. A pair of kidney-shaped ports 41a and 41 b is also open on motor mounting surface 41 to take in ordischarge oil in cylinder block 44. Within center section 25 areprovided a straight oil passage 25 a and an L-like-shaped oil passage 25b for connecting kidney-shaped ports 40 a and 41 a, and 40 b and 41 bwith each other, respectively, to circulate the operating oil betweenthe hydraulic pump and hydraulic motor, thereby making a closed circuit.

The hydraulic pump and hydraulic motor are fluidly connected with eachother through the above-mentioned closed circuit, and the combination ofthese members forms a hydraulic stepless speed change transmission.Capacity of the hydraulic pump is changed by rotatably operating controllever 35 a, thereby enabling the hydraulic motor to obtain steplessoutput rotation.

Operating oil supply means is provided for replenishing oil that hasleaked out from center section 25. The supply means may be the hydraulicpump itself, or a charge pump 31.

Charge pump 31, as shown in FIGS. 5 and 7, is a trochoid pump which iscontained in a charge pump casing 30 attached to a charge pump mountingsurface 43 formed on the lower surface of center section 25. A wavewasher 34 is interposed between a stepped portion at the outer peripheryof charge pump casing 30, and a bottom surface of a lid 33 that closesan opening 223 in lower half housing 22. Wave washer 34 biases chargepump 31 so that charge pump 31 is in contact with charge pump mountingsurface 43. The lower end of pump shaft 29 passes through center section25 and projects from charge pump mounting surface 43, and a pin 29 a ismounted on shaft 29. An engaging bore is open at the center of aninternal gear of charge pump 31. The lower end of pump shaft 29 isinserted into the engaging bore, and pump shaft 29 engages with theinternal gear. Charge pump 31 is fixed to the lower end of pump shaft 29and is driven by pump shaft 29.

Charge pump casing 30 is disposed in an oil sump formed by the housing.A suction port 30 a of charge pump 31 is open at the lower surface ofcharge pump casing 30. Suction port 30 a connects with the oil sump inthe housing through a groove 33 a formed by partially cutting out a wavewasher mounting portion at lid 33. An annular oil filter 32 is fixedbetween charge pump mounting surface 43 and the bottom surface of lid33. Since oil filter 32 surrounds charge pump 31 and charge pump casing30, existing oil is cleaned and then taken in by charge pump 31 throughgroove 33 a and suction port 30 a. When oil filter 32 is maintained andinspected, lid 33 is removed from lower half housing 22, and oil filter32 is removed from the housing through an opening 223 of lower halfhousing 22, oil filter 32 being smaller in outline than opening 223.

The pressure oil discharged from charge pump 31 is directly guided intoa supply oil passage 25c open in charge pump mounting surface 43. If theintroduced pressure exceeds the pressure corresponding to a biasingforce of the wave washer biasing means, the pressure causes charge pumpcasing 30 to move away from or detach from charge pump mounting surface43 against the biasing force of wave washer 34. This creates a gapbetween charge pump 31 and charge pump mounting surface 43. Pressure oilis then released in part from the gap into the oil sump to adjust itspressure below the biasing force of wave washer 34. Charge pump 31 isdetached from charge pump mounting surface 43 to adjust the dischargepressure below the biasing force while maintaining fluid communicationbetween the discharge port and the oil supply port.

As shown in FIG. 8, due to the form of center section 25, pump mountingsurface 40 is positioned in the second plane P2 in upper half housing21, in parallel to and spaced apart by a height H1 from the first planeP1 coincident with the joint surface of the housing. Hence, a wide spaceis formed between charge pump mounting surface 43 positioned opposite topump mounting surface 40, and the inner surface of the bottom of lowerhalf housing 22. As a result, charge pump 31 and oil filter 32 can becontained in this space with ample room. Height H2 from the axis of theaxles to the bottom of lower half housing 22 is reduced to ensuresufficient ground clearance.

As shown in FIG. 9, check valves 50 are disposed at the open ends of oilpassages 25 a and 25 b in the closed circuit of center section 25. Checkvalves 50 mutually communicate at the inlet ports through one transversepassage 25 d. Transverse oil passage 25 d communicates at theintermediate portion with a supply oil passage 25 c open at charge pumpmounting surface 43 of center section 25. Oil introduced from thedischarge port of charge pump 31 to supply oil passage 25 c reaches theinlet side of each check valve 50. The oil pressure pushes out checkvalves 50, positioned at the low pressure side of oil passages 25 a and25 b, so that oil is supplied from the outlet side into the closedcircuit.

Check valves 50 are slidably provided with push pins 51 that projectoutward from center section 25. An axial end of each push pin 51 comesin contact with a single connecting plate 52 in the housing, and arelease rod 53 is fixed at the center of connecting plate 52. Releaserod 53 projects outwardly from upper half housing 21 at one end.Connecting plate 52 is outwardly biased by a spring 54 interposedbetween plate 52 and center section 25. Release rod 53 is manuallypushed in, so that push pins 51 simultaneously push out check valves 50so that the inlet port is in fluid communication with the outlet port.Hence, oil passages 25 a and 25 b communicate with each other throughtransverse oil passage 25 d, thereby enabling the hydraulic motor toidle.

As shown in FIGS. 4 and 8, motor shaft 24 is disposed in parallel toaxles 17 and 18. A counter shaft 26 is provided between the axles andmotor shaft 24, and extends in parallel to the axles and motor shaft 24.A gear 240 is provided on motor shaft 24 and engages with a largerdiameter gear 46 fixed onto counter shaft 26. A smaller diameter gear 47on counter shaft 26 engages with a ring gear 48 of differential gear 23.Thus, a driving force output from motor shaft 24 is transmitted to axles17 and 18 through a gear system speed reduction transmission anddifferential gear 23.

As shown in FIG. 4, a braking friction plate 63 is fixed on motor shaft24, an arm 64 is fixed to upper half housing 21, and a brake actuator 65is provided at one end of arm 64. An operating lever (not shown) isrotated to bring brake actuator 65 in press contact with brakingfriction plate 63, thereby enabling motor shaft 24 to be braked.

The axis of counter shaft 26 is positioned in the first plane P1. It issupported at both axial ends by a pair of bearings interposed betweenupper half housing 21 and lower half housing 22.

As shown in FIG. 8, a pocket projects from the bottom of lower halfhousing 22 to define height H2. The lower portion of larger diametergear 46 on counter shaft 26 is contained within this pocket.

The axes of axles 17 and 18 may be disposed in the first plane P1.However, it is preferable to dispose the axes above the first plane P1as shown in this embodiment. This is because, even when a large diameterinput gear 48 is used in order to enlarge the last gear ratio, the lowerportion of input gear 48 will not extend lower than the lower portion oflarger diameter gear 46. Therefore, the pocket for gear 46 need not befurther enlarged, thereby enabling height H2 to be as small as possibleso that ground clearance is ensured.

As shown in FIG. 4, differential gear unit 23 is displaced in thehousing toward part 18 a of second axle 18. A space is thereby formed atone lateral side of a second axle holder. The larger diameter gear 46 ispartly disposed in this space so that the length of the housing does nothave to be increased.

As shown in FIG. 8, a partition 214 for covering an upper portion ofinput gear 48 is integrally formed in upper half housing 21 and an oilflow-through bore 215 is formed at partition 214. An opening 216 isformed at a portion of the upper wall of upper half housing 21positioned above partition 214, and covered with a cover member 55.Cover member 55 is provided with a breather 56 and an oil check rod 57that is also used as an oil charge plug. A predetermined amount of oilis charged into the housing through cover member 55 so that the boundaryof oil and air is formed in a space enclosed by partition 214 and covermember 55. Air mixed in the oil when charged into the housing iscollected in an air reservoir through oil flow-through bore 215.Partition 214 is filled at the lower portion with oil, so that, evenwhen the various gears rotate, the air in the air reservoir is scarcelymixed in the oil. When the axle driving unit is operated for a longtime, the oil volume expands. The volume of air in the air reservoirdecreases to accommodate the expanded volume of oil.

A second embodiment of the axle driving unit is shown in FIGS. 12-16.The second embodiment is almost the same in construction as the firstembodiment so that the same parts are designated with the same referencenumerals and the description is omitted. As such, only three points ofdifferent construction will be described.

In the case where a lawn tractor includes a wide space underneath thetractor where the mower is disposed, the enlarged region of the housingis extended forwardly as much as possible. The width of the housing ismade as small as possible, thereby enabling the grass chute to increasein volume.

Therefore, a first difference is to elongate the enlarged region of thehousing, and to suitably form center section 25 for such an enlargedregion. Pump mounting surface 40 and motor mounting surface 41, formedon upper surface 250 and side surface 251 of center section 25, areformed so that motor mounting surface 41 laterally overlaps pumpmounting surface 40 by a length L2. As a result, center section 25 canbe contained in the enlarged region having width Wa (see FIG. 12).Cylinder block 36 of the hydraulic pump is disposed further away fromaxles 17 and 18 than in the first embodiment. Length L2 from pump shaft29 to motor shaft 24 is larger in this embodiment (see FIG. 13) than inthe first embodiment (see FIG. 8). There is no overlap OL in thisembodiment as there was in the first embodiment (see FIG. 8).

A third mount boss 210 c is provided at the utmost end of the enlargedregion of the housing. Mount boss 210 c is connected to a third mountingmember (not shown) hanging from body frame 1. Therefore, even when theentire length L1 of the housing becomes larger, the axle driving unitremains in a proper operating position.

A second difference is with respect to motor shaft 24. As in the firstembodiment, braking friction plate 63 is disposed on one end of motorshaft 24 that extends outwardly from the housing. The difference in thisembodiment is that the other end of motor shaft 24 is provided with aspline, and it extends into a through-open bore provided at the centerof motor mounting surface 41. A bushing is interposed between the jointsurfaces of the housing to support a rotary shaft 59 (see FIG. 12). Thespline end of motor shaft 24 is spline-engaged with one end of rotaryshaft 59 so that the driving force of motor shaft 24 is taken out of thehousing through rotary shaft 59.

The outer end of rotary shaft 59 is an indented spline. Braking frictionplate 63 may be mounted on this end of rotary shaft 59, or rotary shaft59 may be used as a power take-out shaft. If such construction is notrequired, rotary shaft 59 can be removed and the bore formed at thejoint surfaces of the housing can be closed by a seal cap.

A third difference is found in the movable swash plate of the hydraulicpump. Movable swash plate 60 of a trunnion-type is used in place of thatof a cradle-type. One trunnion shaft 60 a of movable swash plate 60 issupported by a lid 38 mounted to upper half housing 21, the othertrunnion shaft 60 b being supported by a bearing bore provided at theinner wall of upper half housing 21 (see FIG. 14). Trunnion shaft 60 aprojects outwardly from lid 38 and a control lever 35 a is mounted ontothe projection.

A third embodiment of the axle driving is shown in FIGS. 17-19. Theconstruction of the third embodiment compares to that of the secondembodiment as follows.

Center section 25 is not connected to upper half housing 21 by bolts,but inserted in part between upper half housing 21 and lower halfhousing 22. Therefore, center section 25 is positioned in the enlargedregion in a free-standing state. Housing mounting faces 42′ project fromthe left and right side surfaces 251. The upper surface of centersection 25 and the lower surface opposite thereto form housing mountingfaces. Since center section 25 is free-standing, bolts are not requiredso that assembly is simplified and manufacturing cost is lowered.

In order for center section 25 to be free-standing, pump shaft 29 andmotor shaft 24 are completely supported by the housing. Upper end ofpump shaft 29 is supported by a bearing 104 attached to upper halfhousing 21. Lower end of pump shaft 29 passes through mounting surface40 and charge pump mounting surface 43 and is supported by a bearing 105attached to lower half housing 22 (see FIG. 18). Motor shaft 24 passesthrough motor mounting surface 41 and the two ends are supported bybearings 106 and 107 inserted between both upper half and lower halfhousings 21 and 22 (see FIG. 17).

In the axle driving unit of an embodiment to be discussed below, as inthe second and third embodiments, the enlarged region is made aselongated as possible in order to allow greater volume for the chute ofthe rear discharge lawn tractor.

A fourth embodiment of the axle driving unit will be described inaccordance with FIGS. 20, 21 and 22. A center section 25 ofsubstantially L-like shape in sectional side view is disposed in anelongated enlarged region extending across upper half housing 21 andlower half housing 22, and is fixed to upper half housing 21. A pumpmounting surface 40 is formed on a substantially horizontal uppersurface 250, and a motor mounting surface 41 on a substantially verticalside surface 251 of center section 25. Pump mounting surface 40 ispositioned apart from axles 17 and 18, and motor mounting surface 41 ispositioned near the axles. Pump shaft 29 extends substantiallyvertically with respect to axles 17 and 18, and motor shaft 24 extendssubstantially horizontally with and perpendicular to axles 17 and 18.

A movable swash plate 28 at the hydraulic pump is of a cradle-type anduses the same operating mechanism as that in the first embodiment sothat it is manually controllable along a concave circular-arc surface ofan inner wall of upper half housing 21.

An oil filter 32 is interposed between the lower surface of centersection 25, opposite to pump mounting surface 40, and the inner surfaceof the bottom wall of lower half housing 22. Oil in the housing isfiltered by oil filter 32 and guided to a supply port (not shown) openat the lower surface of center section 25.

A pair of kidney-shaped ports 40 a and 40 b open at pump mountingsurface 40, and a pair of kidney-shaped ports 41 a and 41 b open atmotor mounting surface 41 are connected with each other through a pairof substantially L-like-shaped oil passages 25 a and 25 b, respectively.As shown in FIG. 9, check valves are disposed at the open ends of oilpassages 25 a and 25 b. In this embodiment, operating oil is supplied byoperation of the hydraulic pump itself, but a charge pump as describedin the previous embodiments may alternatively be used.

The axis of motor shaft 24 is positioned in the same plane as the jointsurface of the housing. Motor shaft 24 is rotatably supported bybearings interposed between upper half housing 21 and lower half housing22.

First axle 17 and part 18 a of second axle 18 are rotatably supported bylower half housing 22. Distal portions of first axle 17 and part 18 a ofsecond axle 18 are supported by bearings 100 held into cylindrical boresof lower half housing 22. The bases of axles 17 and 18 are supported bybushings 101 disposed in lower half housing 22. Bushings 101 are fixedlyinterposed between legs 217, long enough to extend beyond the jointsurface of the housing, and the concave circular-arc surface of lowerhalf housing 22 (see FIG. 22).

Differential gear 23 is displaced toward part 18 a of second axle 18 inthe housing. Motor shaft 24 is substantially perpendicular to first axle17, and passes above axle 17 as it extends toward the rear of thehousing. The utmost end of motor shaft 24 projects from the housing, anda braking friction plate 63 is attached to the utmost end of motor shaft24.

A counter shaft 26, extending in parallel to axles 17 and 18, isdisposed at the rear of the housing. The axis of shaft 26 is positionedin the same plane as the joint surface of the housing. Shaft 26 isrotatably supported by bearings sandwiched between upper half housing 21and lower half housing 22.

Since motor shaft 24 and counter shaft 26 are substantiallyperpendicular to each other, a smaller diameter bevel gear 240 a onmotor shaft 24 and a larger diameter bevel gear 46 a, engageable withbevel gear 240 a, on counter shaft 26 are used to connect the shaftstogether in a driving manner. The driving force is transmitted from asmaller diameter gear 47 on counter shaft 26 to axles 17 and 18 througha ring gear 48 on differential gear 23.

A fifth embodiment of the axle driving unit will be described inaccordance with FIGS. 23, 24 and 25. Center section 25, disposed in anelongated enlarged region of the housing, has a substantially flat body.Center section 25 is attached to a side of upper half housing in asubstantially horizontal manner. Pump mounting surface 40 and motormounting surface 41 are formed on upper surface 250 of center section25; the former is positioned apart from axles 17 and 18 and the latteris positioned near the axles. Pump shaft 29 of the hydraulic pump andmotor shaft 24 of the hydraulic motor extend in parallel to each other,and are substantially vertical, being at a right angle to axles 17 and18.

A pair of kidney-shaped ports 40 a and 40 b open at pump mountingsurface 40, and a pair of kidney-shaped ports 41 a and 41 b open atmotor mounting surface 41 are connected to each other through a pair ofstraight oil passages 25 a and 25 b.

Movable swash plate 28 of the hydraulic pump is of a cradle-type, and ismanually controllable along the concave circular-arc surface of theinner wall of upper half housing 21 by use of an operating mechanism asin the first embodiment. A fixed swash plate 45 of the hydraulic motoris fixedly fitted into a concave formed at the inner wall of upper halfhousing 21.

Pump shaft 29 and motor shaft 24 are rotatably supported by bearingslongitudinally juxtaposed at upper half housing 21, and bearingslongitudinally juxtaposed at center section 25.

A counter shaft 26 is disposed in the same plane as the joint surface ofthe housing. A pair of bearings for supporting counter shaft 26 aresandwiched between a pair of legs 252 downwardly projecting from thelower surface opposite to motor mounting surface 41, and a pair of legs224 upwardly projecting from the inner surface of the bottom wall oflower half housing 22 (see FIG. 23). With this construction, there is noneed for a bearing holding portion for counter shaft 26 to be providedat the housing. Therefore, the width Wa of the enlarged region can befurther restricted (see FIG. 24). One end of counter shaft 26 projectsoutwardly from the housing for attachment of a braking friction plate63.

A substantially vertical motor shaft 24 passes downwardly through centersection 25. The lower end portion of motor shaft 24 is positioned justabove, and at about a right angle to, the axis of the axles (see FIG.25). A small diameter bevel gear 240 a is fixed on the lower end ofmotor shaft 24, and a larger diameter bevel gear 46, engageable withbevel gear 240 a, is fixed on counter shaft 26, thereby connectingshafts 24 and 26.

A driving force is transmitted from a smaller diameter gear 47 oncounter shaft 26 to a ring gear 48 of differential gear 23, differentialgear 23 being displaced toward part 18 a of axle 18 in the housing. Theaxes of axles 17 and 18 are positioned in the same plane as the jointsurface of the housing. The terminal and bore of first axle 17 aresupported only by bearing 100 and bushing 101 interposed between upperhalf housing 21 and lower half housing 22. Differential gear 23 iseccentrically disposed to further reduce the axial length of part 18 aof second axle 18 so that part 18 a of second axle 18 is supported byonly bushing 101 sandwiched between upper half housing 21 and lower halfhousing 22.

A sixth embodiment of the axle driving unit will be described inaccordance with FIGS. 26, 27 and 28. The construction is basically thesame as that of the fifth embodiment so that only the following fourpoints are described which are different from that of the fifthembodiment.

A first modified point is the position of braking friction plate 63. Theupper end of substantially vertical motor shaft 24 passes through theupper wall of upper half housing 21, and braking friction plate 63 ismounted to this upper end. This allows the braking device to be smallerand more compact because motor shaft 24 has a lower transmitting torquethan counter shaft 26. As a result, the axle driving unit becomessmaller in width. Braking friction plate 63 is disposed on the same sideas pump shaft 29 that projects from the housing, and is in proximity tocooling fan 16. This enables friction plate 63 to be effectively cooledby the ventilation from cooling fan 16. The ventilation from cooling fan16 also blows away the dust collected on braking friction plate 63.

A second modified point is with respect to center section 25. One leg252 downwardly projects from the surface of center section 25 oppositeto motor mounting surface 41. Leg 252 and lower half housing 22 supporta bearing for the end of counter shaft 26, and a bearing at the otherend of counter shaft 26 is sandwiched between upper half housing 21 andlower half housing 22. Leg 252 may be formed separately from centersection 25 and fixed below its plane.

A third modified point is with respect to differential gear 23′. Aninput gear 48′ of differential gear 23′ is freely fitted on part 18 a ofsecond axle 18, and is disposed in proximity to one side wall of thehousing, thereby considerably reducing the axial length of part 18 a ofsecond axle 18. A differential case 48 a is attached to the oppositeside wall of the housing. In differential case 48 a, the base ends offirst axle 17 and part 18 a of second axle 18 abut against each other.Side gears 49 engage with pinions 50 pivoted to the base sides of firstaxle 17 and part 18 a of second axle 18.

A fourth modified point is in the layout of first axle 17 and part 18 aof second axle 18 and the construction of the housing support withrespect to the joint surface of the housing. The axes of axles 17 and 18can be disposed in substantially the middle portion of the height of thehousing and still retain the balance of the axle driving unit. Theprotrusion formed in the bottom portion of lower half housing 22 forinput gear 48′ can thus be made smaller in volume to ensure sufficientheight from the ground.

A seventh embodiment of the axle driving unit will be described inaccordance with FIGS. 29, 30 and 31.

Center section 25, as in the fifth and sixth embodiments, issubstantially shaped like a flat plate, and mounted to upper halfhousing 21. The body of center section 25 is substantially horizontallydisposed in lower half housing 22. Pump mounting surface 40 is formed onthe substantially horizontal upper surface of center section 25 spacedapart from axles 17 and 18. Motor mounting surface 41 is formed on thesubstantially horizontal lower surface of center section 25 in proximityto axles 17 and 18.

Motor shaft 24 of the hydraulic motor is journalled at its upper end tocenter section 25, and at its lower end to lower half housing 22. If itis difficult to mount the hydraulic motor onto motor mounting surface41, the lower end of motor shaft 24 may be journalled to a fixed swashplate 45, and fixed swash plate 45 may be connected to the lower surfaceof center section 25.

Motor shaft 24 extends in parallel to pump shaft 29, and substantiallyvertically passes through the upper wall of center section 25. On theupper end of motor shaft 24 is fixed a smaller diameter bevel gear 240 aengageable with a larger diameter bevel gear 46 a on counter shaft 26.

In order to support counter shaft 26 in the same plane as the jointsurface of the housing, a pair of bearings is provided between a pair oflegs 252′, upwardly projecting from the surface of the center sectionopposite to motor mounting surface 41, and a pair of legs 218 projectingfrom the inner wall of upper half housing 21.

Although several embodiments have been described, they are merelyexemplary of the invention and not to be construed as limiting, theinvention being defined solely by the appended claims and theirequivalents.

What is claimed is:
 1. A lawn tractor comprising: a body frame havingtwo sides, a forward portion and a rear portion; a prime mover disposedon said body frame; a first driving wheel disposed on one of the twosides of said body frame; a second driving wheel disposed on the otherof the two sides of said body frame; a housing eccentrically disposedtoward one of the two sides of said body frame; a first axle projectingfrom said housing for mounting thereon said first driving wheel; asecond axle projecting from said housing for mounting thereon saidsecond driving wheel, said second axle longer in length than said firstaxle; a hydrostatic transmission including a hydraulic pump with aninput shaft and a hydraulic motor, said hydrostatic transmissioninputting a driving force from said prime mover through said input shaftand steplessly changing the speed of the driving force for outputting tosaid first axle and said second axle; a mower disposed beneath said bodyframe and driven by said prime mover; a catcher attached to the rearportion of said body frame; and a longitudinally extending chuteattached to said body frame, wherein said chute extends above saidsecond axle where said chute and said second axle cross to guide lawngrass cut by said mower into said catcher, and wherein said housingextends toward the forward portion of said body frame in parallel tosaid chute.
 2. A lawn tractor according to claims 1, further comprising:a first mount boss disposed on a first side of said housing from whichsaid first axle projects; a second mount boss disposed on a second sideof said housing from which said second axle projects; a first mountingmember attached to said body frame adjacent to said first driving wheel;a second mounting member attached to said body frame between said firstand said second driving wheels; and wherein said first mount boss iscoupled to said first mounting member and said second mount boss iscoupled to said second mounting member to thereby mount said housing tosaid body frame in an operating position.
 3. A lawn tractor according toclaim 1, further comprising: a bearing device attached to said bodyframe adjacent to said second driving wheel for rotatably supporting anintermediate portion of said second axle.
 4. A lawn tractor according toclaim 3, wherein said second axle comprises: a first axle part; a secondaxle part for mounting thereon the second driving wheel, said secondaxle part rotatably supported by said bearing device; and a coupling forconnecting said first and said second axle parts.
 5. A lawn tractoraccording to claim 1, further comprising: a pair of bearing holdersdisposed in said housing, one of said pair supporting the distal portionof said first axle and the other of said pair supporting the distalportion of said second axle, wherein the distance between said pair ofbearing holders defines the width of said housing to be less than thelength of said housing including said enlarged region.
 6. A lawn tractoraccording to claim 1, further comprising: a mower discharge port formedin said mower, wherein said mower discharge port is eccentricallydisposed toward the other of the two sides of said body frame away fromsaid housing.
 7. A lawn tractor comprising: a body frame having twosides, a forward portion and a rear portion; a prime mover disposed onsaid forward portion of said body frame; a first driving wheel disposedon one of the two sides of said body frame; a second driving wheeldisposed on the other of the two sides of said body frame; a housingeccentrically disposed toward one of the two sides of said body frame,said housing including a differential; a first axle projecting from saidhousing for mounting thereon said first driving wheel, said first axlebeing driven by said differential; a second axle projecting from saidhousing for mounting thereon said second driving wheel, said second axlebeing longer in length than said first axle and being driven by saiddifferential; a hydrostatic transmission, said hydrostatic transmissionincluding a hydraulic pump and a hydraulic motor, said hydrostatictransmission inputting a driving force and steplessly changing the speedof the driving force for outputting to said differential; a mowerdisposed beneath said body frame and driven by said prime mover; acatcher attached to said rear portion of said body frame; and alongitudinally extending chute attached to said body frame, said chuteguiding lawn grass cut by said mower into said catcher, wherein saidhydrostatic transmission is disposed adjacent to said chute.
 8. A lawntractor comprising: a body frame having two sides, a forward portion anda rear portion; an engine having a vertical crank shaft disposed on saidbody frame; a first driving wheel disposed on one of the two sides ofsaid body frame; a second driving wheel disposed on the other of the twosides of said body frame; a housing eccentrically mounted to said bodyframe in proximity to said first driving wheel; a first axle projectingfrom said housing for mounting thereon said first driving wheel; asecond axle projecting from said housing for mounting thereon saidsecond driving wheel, said second axle being longer in length than saidfirst axle; a differential disposed within said housing fordifferentially connecting said first axle and said second axle; ahydrostatic transmission including a hydraulic pump and a hydraulicmotor, said hydrostatic transmission being disposed within said housingand drivingly connected to said differential; an input shaft forinputting a driving force into said hydraulic pump from said engine,said input shaft being substantially vertically projecting from an uppersurface of said housing; a mower disposed beneath said body frame anddriven by said engine; a catcher attached to the rear portion of saidbody frame; a longitudinally extending chute attached to said body framefor guiding lawn grass cut by said mower, wherein said housing extendstoward the forward portion of said body frame in parallel to said chute;and a transmitting means for connecting said engine to said hydraulicpump, disposed in parallel to said chute.
 9. A lawn tractor according toclaim 8, further comprising: bearing means disposed in said housing forsupporting said first and said second axles, said bearing meanscomprising a pair of bearing holding members, one of said pairsupporting the distal portion of said first axle and the other of saidpair supporting the distal portion of said second axle, wherein thedistance between said pair of bearing holding members defines the widthof said housing to be less than the length of said housing includingsaid enlarged region.
 10. A lawn tractor according to claim 8, furthercomprising: a bearing device attached to said body frame adjacent tosaid second driving wheel for rotatably supporting an intermediateportion of said second axle.
 11. A lawn tractor according to claim 8,wherein said second axle comprises: a first axle part; a second axlepart for mounting thereon the second driving wheel; a coupling forconnecting said first and said second axle parts; and a bearing deviceattached to said body frame for supporting said second axle part.
 12. Alawn tractor according to claim 8, wherein said hydraulic pump isdisposed in said housing so that a rotary axis of said hydraulic pump ispositioned on a rotary axis of said input shaft, and said hydraulicmotor is disposed in said housing such that said hydraulic motor iscloser to said first and second axles than said hydraulic pump is.
 13. Alawn tractor according to claim 8, wherein said input shaft iseccentrically disposed toward said first axle.
 14. A lawn tractorcomprising: a body frame having two sides and a rear portion; a primemover disposed on said body frame; a first driving wheel disposed on oneof said two sides of said body frame; a second driving wheel disposed onthe other of said two sides of said body frame; a housing including adifferential; a shaft projecting from said housing towards one of saidfirst and second driving wheels driven by said differential; a mowerdisposed beneath said body frame and driven by said prime mover; acatcher attached to said rear portion of said body frame; and alongitudinally extending chute attached to said body frame, said chuteguiding grass cut by said mower into said catcher, wherein said housingis disposed laterally to said chute and said chute extends above saidshaft where said chute and said shaft cross.
 15. A lawn tractoraccording to claim 14, wherein said housing is eccentrically disposedtoward one of said two sides of said body frame.
 16. A lawn tractoraccording to claim 14, further comprising a hydrostatic transmission forinputting power from said prime mover and outputting to saiddifferential.